1. Field of the Invention
The present invention relates to airbag inflation systems for use in motor vehicles. More specifically, the present invention relates to airbag inflator housings for diffusing inflation gas exiting an airbag inflator.
2. Description of Related Art
Safety belts are designed to protect the occupants of a vehicle during events such as automobile collisions. In low-speed collisions, the occupants are generally protected from impact with objects located inside the vehicle such as the windshield, the instrument panel, a door, the side windows, or the steering wheel by the action of the safety belt. In more severe collisions, however, even belted occupants may experience an impact with the car's interior. Airbag systems were developed to supplement conventional safety belts by deploying into the space between an occupant and an interior object or surface in the vehicle during a collision event. The airbag acts to decelerate the occupant, thus reducing the chances of injury to the occupant caused by contact with the vehicle's interior.
Many typical airbag systems consist of several individual components joined to form an operational module. Such components generally include an airbag cushion, an airbag inflator, a sensor, and an electronic control unit. Airbag cushions are typically made of a thin, durable fabric that is folded to fit into a compartment of a steering wheel, dashboard, interior compartment, roof, roof rail, roof compartment, or other space in a vehicle. The airbag inflator is designed to produce a gas to rapidly inflate the cushion when needed. The sensors detect sudden decelerations of the vehicle that are characteristic of an impact. The readings taken by the sensors are processed in the electronic control unit using an algorithm to determine whether a collision has occurred.
Upon detection of an impact of sufficient severity, the control unit sends an electrical signal to the inflator. The inflator uses one of many technologies, including pyrotechnic compounds and pressurized gas, to produce a volume of an inflation gas. The inflation gas is channeled into the airbag, rapidly inflating it. Inflation of the airbag causes it to deploy, placing it in position to receive the impact of a vehicle occupant. After contact of the occupant with the airbag and the corresponding deceleration of the occupant, the airbag rapidly deflates. To accomplish this, the inflation gas is vented from openings in the airbag, deflating it and freeing the occupant to exit the vehicle.
Airbag apparatuses have been primarily designed for deployment in front of an occupant: between the upper torso and head of an occupant and the windshield or instrument panel. Side impact airbags such as inflatable curtains and seat mounted airbags also have been developed in response to the need for protection from impacts in a lateral direction, or against the side of the vehicle. Other airbags such as knee bolsters and overhead airbags also operate to protect various parts of the body from collision.
Generally, the inflator is installed within or in close proximity to the textile airbag. However, doing so requires the inflator to be housed in a diffuser. When activated, the inflator generates inflation gas which escapes exit ports in the inflator at a high velocity and temperature. Due to limited space, the uninflated textile bag is often folded up against the inflator. Without a diffuser, the hot gas is concentrated on the textile bag. The concentrated hot gas and the confined space may combine to cause the gas to burn one or more holes in the textile bag. The holes may cause the airbag to inflate improperly.
A diffuser housing disperses the inflation gas, allowing them to expand and cool. Heat may be transferred from the inflation gas to the surface of the diffuser. A diffuser may also be used to direct the gas leaving the exit ports. However, in order for the inflator to perform properly, a flow area around the inflator is needed to enable inflation gas to exit the inflator without excessive restriction. The needed flow area is achieved through the existence of an exhaust passage. Exhaust passages are typically a space between the inflator and the diffuser housing. Gas may be directed through the exhaust passage to cause the airbag to inflate in a particular manner. Once the gas passes through the diffuser, the gas is sufficiently cooled and/or not concentrated to prevent burning holes in the textile airbag.
For example, in a side impact airbag module, an inflator is typically press-fitted inside a steel housing with pre-installed mounting studs extending therefrom. The inflator housing and side airbag are then ordinarily enclosed in a plastic case having two sides that snap together. The resulting module is a thin rectangular or alternatively-shaped module enclosing the inflator, inflator housing, and side impact airbag.
In order for the inflator to perform properly, an exhaust passage must exist between the housing and the inflator to provide a flow area for inflation gas to exit the inflator. An exhaust passage is typically created by press-fitting the inflator against pre-formed inwardly directed dimples in the steel housing. A press fit is an interference force fit accomplished using a press. A heavy press fit, where the inflator is tightly pressed into the steel housing, is often necessary to prevent axial movement of the inflator within the housing. The axial direction is parallel to the longitudinal length of the inflator. The inflator is thereby in contact with the inwardly directed dimples while the remaining surface of the steel housing is spaced apart from the inflator a short distance. The space between the inflator and the steel housing comprises the exhaust passage. However, the existence of the exhaust passage widens the profile of the inflator housing in a direction orthogonal to the direction the mounting studs project. The side impact airbag module may consequently protrude out of the side of the seat when installed.
Exhaust passages typically occupy valuable space when the diffuser and inflator are installed and not in use. Uninflated airbag modules are installed in a very limited space in a steering wheel, dashboard, interior compartment, seat back, roof rail, roof compartment, or other space in a vehicle. Consequently, the minimization of the space occupied by the exhaust passages may provide an aesthetically pleasing installation area and give vehicle manufacturers more flexibility in designing the installation area.
Accordingly, a need exists for an airbag diffusion system which cools the inflation gas exiting the inflator to prevent holes from being burned in the airbag material. A need further exists for the airbag diffusion system to be compact and have a thin profile to allow the system to be installed in areas of small dimensions relative to conventional diffusion systems. A need also exists for a diffusion system to be simple and inexpensive to fabricate. Such an apparatus is disclosed herein.